Organic EL devices, which utilize emission of organic compounds, are known.
Such an organic EL device includes a plurality of organic thin films layered between an anode and a cathode. In this structure, voltage is applied between the anode and cathode. Then, holes and electrons are injected into the organic thin films respectively from the anode and cathode. The injected holes and electrons generate excited-state molecules in an emitting layer within the organic thin films. Energy generated when the molecules return to the ground state from the excited state is emitted as light.
As an emitting material having high luminous efficiency, high luminance and excellent color purity, pyrene derivatives are known (e.g., Patent Document 1).
However, pyrene skeletons exhibit high crystallinity due to their high planarity, so that crystallization tends to progress during an amorphous thin-film state and driving of the device. Destruction of thin films by crystallization leads to reduction in luminance or non-emission. When planarity of molecules is high, molecular aggregate is easily generated. Fluorescence obtained from molecular aggregate is unfavorably of longer wavelength than fluorescence obtained from a single molecule.
In view of the above, a known method makes a pyrene derivative sterically bulky by introducing substituents in the pyrene skeleton and thereby suppresses crystallization and molecular aggregate.
For instance, Patent Document 2 discloses diaminopyrene derivatives, and Patent Document 3 discloses diaminopyrene derivatives in which alkyl groups or aryl groups are introduced into the pyrene skeletons.    Patent Document 1: JP-A-2002-063988    Patent Document 2: JP-A-2004-204238    Patent Document 3: WO2005/108348